Unassisted Highly Selective Gas-Phase CO₂ Reduction with a Plasmonic Au/p-GaN Photocatalyst Using H₂O as an Electron Donor

Abstract

Surface plasmon resonances in metal nanostructures enable the generation of nonequilibrium hot electron–hole pairs, which has received wide interest as a means to drive chemical reactions at the nanoscale. However, harvesting hot holes in plasmonic heterostructures to drive oxidation reactions to balance the photocatalytic CO2 reduction reaction has been challenging. Further, details of the balanced redox reaction pathways for gas-phase photocatalysis have been difficult to identify. Here, we report an Au/p-GaN plasmonic heterostructure photocatalyst in which unassisted, self-sustaining, highly selective photocatalytic CO2 reduction to CO is directly balanced by water oxidation, operating under solar illumination. We find remarkable enhancements in CO yield for heterostructures that employ a metal/insulator/semiconductor configuration with an ultrathin aluminum oxide layer between composite Au/Cu nanoparticles and p-GaN. Our work underscores the potential for plasmonic heterostructure photocatalysts to perform selective and unassisted gas-phase photocatalytic CO2 reduction to convert solar energy into chemical fuels.

Recent Progress and Challenges in Plasmon‐Mediated Reduction of CO2 to Chemicals and Fuels

“…[ 108 ] Recently, a self‐sustaining composite of Au/p‐GaN was fabricated with an Al 2 O 3 interfacial layer and further deposition of Cu on Au surface (Au‐Cu/Al 2 O 3 /p‐GaN) ( Figure a). [ 135 ] The system was able to perform CO 2 photoreduction without any external energy inputs. The Al 2 O 3 layer was found to be passivating the surface defects that originally served as electron‐hole recombination centers.…”

“…[145] The plasmonic activity of modified Ag nanoparticles has been availed for CO 2 [135] a,b) Reproduced with permission. [135] Copyright 2021, American Chemical Society.…”

“…As such significant enhancement in CO production rate (up to 69% for Au/Al 2 O 3 /p‐GaN system) was achieved mainly because of Al 2 O 3 passivation (optimum thickness 1 nm) and the favorable CO 2 surface chemistry on Cu nanoparticles (Figure 13b). [ 135 ] This way, exploiting hot electrons and holes in photochemical reactions offers meticulous research opportunities for future developments. Engineering hybrid plasmonic nanocomposites with innovative designs, such that taking care of the multicomponent systems and the precise geometries of both the plasmonic and non‐plasmonic systems holds great promise to achieve maximum charge separation and CO 2 conversion efficiency.…”

Heterogeneous Catalysis for CO2 Conversion into Chemicals and Fuels

“…To improve the performance of photocatalytic/PEC CO 2 reduction, the construction of heterostructure photocathodes comprising multiple components is an important approach. Li and coworkers [190] developed an Au/p-GaN plasmonic heterostructure photocatalyst for selective and unassisted gas phase photocatalytic CO 2 reduction to CO under visible-light illumination. A metal/insulator/ semiconductor configuration with a nanometer-thick aluminum oxide layer between Au/Cu NPs and p-GaN could remarkably improve the CO production rate (Fig.…”

Recent advances in photocatalytic renewable energy production

“…Li et al [120] incorporated the heteroatom B-Co dimer into a porous C 2 N to form B-Co@C 2 N, which was used for the photoreduction of CO 2 to C 2 H 6 . The combination of B and Co regulated the 3d orbital of the Co atoms to a lower energy level, which impairs the CO adsorption strength in comparison with Co-Co@C 2 N and results in a low energy barrier of ~0.61 eV for C-C coupling.…”